Diameter: About 15cm /5.91in Scientific and Reasonable Design and Construction, Easy to Carry, Easy to Use. Inflatable Balls Can Adjust the Size of Their Own, Neck Rope Can Adjust the Length, Suitable for Different Height Golf Enthusiasts. This Inflatable Smart Ball is Connected to an Adjustable Rope to Satisfy Anyone's Needs. It is Currently on the Market a Very Good Training Aids Can Be Used in the Armpit, Can Also Be Inflated Between the Forearm. The Smart Ball Will Help You Understand How the Arm and Body Work During the Effective Golf Swing. Now Control Your Swing, So You Can Have Effortless Power Instead of Weak Effort. Using This Golf Intelligent Inflatable Ball Practitioner Can Correctly Grasp the Swing Posture, Fix and Strengthen the Arm Distance Muscle Memory. Package Include: 1 * Golf Swing Trainer Ball(black), 1 * Inflator .